Picture 1 is the 45 ish degree angle cut. The first cut off the wedge/Humboldt. A horizontal cut (which is the cut in picture 2 that the saw is sitting on) meets the first cut.

In order to cut these extra large trees with smaller bars you extend the second cut into the middle of the tree where those first two cuts meet (picture 2 I made the 3rd cut behind the saw where those two surfaces met and plunge cut out as much of the middle as I could being sure to leave hinge wood on both sides).